Currently, access points (APs) are capable of supporting a large number of associated stations (STAs) (e.g., over 6,000 STAs) which may operate on a very strict energy budget. Such devices may be, for example, battery powered sensors which transmit and receive data very rarely and which stay in the low power operation mode for relatively long periods of time. The basic operation mode of an AP operating according to the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard is the Distributed Coordination Function (DCF) mode. In order to support such a large number of STAs operating in random access mode, an access point(s) may utilize specific techniques to restrict the contention to a channel to avoid collisions of simultaneous transmissions in the collision domain. One such technique to reduce contention and collisions of transmission is a method of grouping STAs to multiple groups and assign certain parameters for each group to indicate the specific group that may access (e.g., content for) the channel. Such grouping information and parameters for the operation may be delivered to the STAs in an association phase or for example in the broadcast information such as beacons.
To further enhance the energy saving of the STAs, a system may incorporate a so-called relay functionality in which intermediate nodes (e.g., relays) may be utilized to receive and forward transmission of STAs. STAs may use lower transmission power to reach the intermediate nodes which may then forward the transmissions to a destination node. Although this may increase the energy consumption of the intermediate node, the intermediate node(s) is usually not energy limited. For example, an intermediate node(s) may be connected to a power supply. Some intermediate nodes such as, for example, relays may be battery powered but it is typically easier to replace the battery of relays instead of the batteries of, for example, several hundred devices (e.g., STAs).
In the IEEE 802.11ah and in the IEEE 802.11 protocols, relays may be used to improve energy consumption and potentially coverage, and specific mechanisms may be used to ensure that relays and STAs have a common understanding as to the manner in which to operate. STAs may spend most of the time in the low power state and as such the relay operation should take this into account.